“Each person in Britain has far more impact on the environment than those in developing countries so cutting our population is one way to reduce that impact.”

Population growth is one of the most politically sensitive environmental problems.

Professor Chris Rapley, director of the Science Museum, will use the OPT conference, to be held at the Royal Statistical Society, to warn that population growth could help derail attempts to cut greenhouse gas emissions.

Rapley, who formerly ran the British Antarctic Survey, said humanity was emitting the equivalent of 50 billion tons of CO2 into the atmosphere each year.

“We have to cut this by 80%, and population growth is going to make that much harder,” he said.

Many experts believe that, since Europeans and Americans have such a lopsided impact on the environment, the world would benefit more from reducing their populations than by making cuts in developing countries.

This is part of the thinking behind the OPT’s call for Britain to cut population to 30m — roughly what it was in late Victorian times.

Some politicians support a reduction.

Phil Woolas, the immigration minister, said: “You can’t have sustainability with an increase in population.”

The Tory leader, David Cameron, has also suggested Britain needs a “coherent strategy” on population growth.